Oscillatory digger



lApril 9, 1963 R. T. LovRENlcH oscILLAToRY BIGGER 2 Sheets-Sheet 1 Filed Sept. 24, 1957 INVENTOR Roose/r Z' owns/wc# April 9, 1963 R. T. LovRENlcl-l 3,084,817

oscILLAToRY BIGGER Filed sept. 24, 1957 2 sheets-sheet 2 INVENTOR.

Romea 7.' omi/vlc# United States Patent O 3,084,817 OSCILLATORY DIGGER Rodger T. Lovrenich, Detroit, Mich., assigner, by mesne assignments, to Ford Motor Company, a corporation f Delaware Filed Sept. 24, 1957, Ser. No. 635,835 6 Claims. (Cl. 214-138) The present invention relates to an oscillatory digger and more particularly to a digger or the like having a hydraulically actuated digging element oscillatable when in contact with the ground or other digging medium to increase the penetration of the digging element therein.

The present invention is particularly useful in conjunction with back hoes or similar digging implements utilized as attachments for standard farm or industrial tractors. Such diggers inherently are limited in digging capacity by the size and weight of the digger which the prime mover can support and convey and by the size and capacity of the prime mover engine which furnishes hydraulic power for the digging apparatus. As a result of such limitations, one serious drawback to the utilization of such diggers has been its lack of penetration ability in extremely hard ground, macadam or concrete roads, and the like. The present invention now provides a new and novel oscillatory apparatus for increasing the penetration capability of a digger of this type.

'More particularly, in the present invention the apparatus of the present invention is utilized to oscillate one of the digger bucket actuation elements at a frequency approximately equal to the resonant mechanical frequency of the tractor and digger assembly. This oscillation can be accomplished in any desired manner, for example, the oscillation can be accomplished by the utilization of a solenoid controlled four-way valve interposed in the bucket actuation circuit or by means of a fourway valve which is oscillated hydraulically. No matter in which way the oscillation is accomplished, the end result is that the prime mover and the digger are caused to oscillate at approximately the resonant frequency of the unit about the bucket digging edge which normally is provided with projected digging teeth. Inasrnuch as the assembly may have a gross weight on the order of 10,000 lbs., it will be appreciated that a substantial 'penetrating force is exerted by the bucket teeth and vastly improved penetration characteristics have been observed in a wide variety of digging media.

The frequency of oscillation is determined by the gross weight and the elastic properties of the digger and prime mover assembly. It has been found that, for an assembly having a gross weight of about 10,000 lbs. and of the design illustrated in the attached drawings, the :mechanical resonant frequency will be on the order of 21/2 cycles per second.

It is, therefore, an important object of the present invention to provide new and improved digging apparatus having enhanced penetration characteristics.

IAnother important object of the present invention is to provide an improved digging apparatus having a groundengageable element oscillatable to increase the penetration characteristics of the digging element in the digging mediurn.

It is still a further object of this invention to provide a digging apparatus including a digger and prime mover assembly which oscillates at the mechanical resonance frequency of the assembly in order to increase the penetration characteristics of the digging element.

Y et another and further object of this invention is the provision of a digging apparatus wherein a ground-engaging digging element is selectively oscillatable at the natural resonant frequency of the apparatus for selectively increasing the penetration ability of the element.

3,084,817 Patented Apr. 9, 1963 Referring now to the drawings:

[FIGURE l is an elevational view of a digging apparatus of the present invention illustrated as employed with a prime mover shown in phantom outline;

CFIGURE 2 is a schematic view illustrating the apparatus for oscillating the digging element;

FIGURE 3 is a view similar to FIGURE 2 illustrating another form of apparatus for oscillating the digging element.

In FIGURE 1, reference numeral 10 refers generally to a prime mover such as an industrial or farm tractor having attached thereto a digging apparatus indicated generally at 11.

The digging apparatus includes a main frame 12 attached to the chasis of the prime mover 10 and provided with an operators seat 13 located rearwardly of the tractor. A control panel 14 is located adjacent the seat 13 and is provided with a plurality of upwardly projecting control levers 15 for controlling various components of the digger as will hereinafter be more fully described.

The main frame 12 carries at its rear extremity an upstanding swing post 16 upon which is supported a lower boom plate 17 oscillatable about the vertical axis of the swing post upon actuation of a pair of transversely spaced swing cylinders 18 carried by the main frame. This boom plate 17 carries a transverse bearing 19 upon which is pivotally disposed an upwardly and rearwardly projecting boom 20. The boom is pivotally connected at its outer end, as at 21, to a depending dipstick 22, the dipstick having pivoted thereto, as at 23, a bucket 24 which forms the ground-engaging element of the digger. The bucket 24 is provided at its lower extremity with a plurality ,of transversely spaced digger teeth 25.

To elevate and lower the boom about its pivot point 19, the boom is pivotally connected, as at 26, to a lift cylinder 27 which is anchored to a swing plate at the upper end of the swing post 16. Interconnecting the swing post 16 and the upper free extremity of the dipstick 22 are a pair of transversely spaced crowd cylinders 28 which serve to actuate the dipstick 22 arcuately about its point 21 of pivotal connection to the boom 20` To effect movement of the bucket 24 relative to the dipstick 22, an actuating cylinder 30 is pivotally anchored to the dipstick, as at 31, and to the bucket through linkage elements 32.

The digger is hydraulically actuated and controlled by means of a hydraulic system including a prime moverdriven pump and a reservoir (not shown) and the hereinbefore described swing cylinders 18, the lift cylinder 27, the crowd cylinders 12'8, and the bucket actuating cylinder 30. In FIGURES 2 and 3, there are illustrated only those portions of the hydraulic circuit which are essential to the operation of the improvement of the present invention.

Referring now to FIGURE 2 of the drawings, reference numeral 40 refers to a pressure fluid line from the prime mover-driven iiuid pump. This line 40 communiv cates with a valve chamber 41 disposed in a valve block 42 located at or adjacent the operators station. The valve block 42 actually includes an entire bank of valves for controlling all of the various digger hydraulic components, but the schematic drawing of FIGURE 2 shows only a portion of the valve block 42. Slidably disposed within the valve chamber 41 is a vertically movable valve body 43 having a pair of spaced lands 44 and 45 separated by a central groove 46. The valve body 43 is reciprocable vertically through a valve stem 47 which is connected to an actuating handle 15 located at the operators station 13. A iluid drain line 48 communicates with the groove 46 of the valve body 43 when the valve body occupies the position illustrated in FIGURE 2 of the drawings.

When the valve body occupies its position of FIGURE 2, it will be seen that the land 44 thereof blocks a conduit 49 leading to a four-way solenoid controlled pilot operated valve 50.

This valve 50 includes a valve body 51 having axially spaced radially enlarged lands 52-55 inclusive, thereupon and `contined in a valve chamber 56. A second iluid conduit 57 interconnects the valve block 42 and the valve chamber 56. The valve body 51 is provided with a pair of radial passages 58 and 59 interconnected by an axial passage 60 to connect the spool portion of the valve body 51 lying intermediate the lands 52 and 53 with that spool portion lying intermediate the lands 54 and 55.

The actuating cylinder 30 has either end thereof connected to the valve chamber 56, as through conduits 61 and 62, the actuating cylinder 30 being of the doubleaeting type and having a piston 30a displaceable axially within the cylinder 30a to project or retract a piston rod Sllb carried thereby.

`Confined between one end of the valve body 55 and the valve chamber 56 is a coil compression spring 63. The other end of the valve body 55 carries a longitudinally extending solenoid core rod 64 cooperable with a solenoid coil 65. The solenoid dened by the core 64 and the coil 65 is of the repulsion type and, when the coil is energized, the valve body 51 is displaced to the right against the compression of the spring 63. To energize the solenoid coil 65, a suitable source of electric energy, such as a battery 66 is utilized, the current ow from the battery 66 to the coil 65 being controlled by a pair of electrical contacts including a xed contact 67 and a camactuated movable contact 68. This latter contact is actuated by a `cam 70 having a semi-circular raised cam surface 71 and a complementary recessed cam surface 72 adapted to be engaged by a follower 73 located on the arm of the contact 68. The cam is rotated by suitable means, as by shaft 74 energized by an electric motor 75 driving a speed changer 76 so that the cam is rotated at a rate consistent with the natural or mechanical resonant frequency of the digger and prime mover unit illustrated in FIGURE l of the drawings.

The operation of the embodiment of the invention illustrated in FIGURE 2 will be readily appreciated by those skilled in the art. Upon elevation of valve spool 43, fluid pressure from the supply line 40 is vented to the conduit 49, while the return conduit 57 is vented to the drain line 48 of the valve block 42 by the same movement of the spool valve 43. Pressure tluid through the line 49 is introduced into the valve chamber 56 intermediate the lands 53 and 54 and through the conduit 61 into the cylinder 30 to extend the actuating cylinder piston rod 30b. Such extension of the rod will, through the linkage 32, rotate the bucket 24 about its pivot point 23 attempting to force the bucket teeth 25 into the digging medium.

If the motor 75 is now energized to drive the cam 70,

closure of the contacts 67 and 68 will energize the solenoid winding '65, and the repulsion solenoid will force the valve body 51 to the right against the compression of the spring 63, thus disconnecting the line 49 from the line 61 and interconnecting the line 49 with the line 62, Initially, the drain line 57 was connected with the line 62 through the radial ports 58 and 59 and axial passage 60 in the valve body 51. However, upon an actuation of the solenoid and consequent displacement of the valve body 51 to the right, the drain line 57 is now connected to the line 61 between the lands 52 and 53. Thus, the piston rod 30b will be retracted within the cylinder 30.

Upon continued rotation ofthe cam 70 until the follower 73 again` engages the recessed portion 72 of the cam periphery, the solenoid windings or coil 65 would be cie-energized, the spring 63 will return the valve body 51 to the illustrated position of FIGURE 2, line 61 will again be connected to the pressure line 49 and the bucket again will be forced into the digging medium.

Assuming that teeth 25 have become engaged in the digging medium, the reversal of fluid pressure on the cylinder 30 will not fully retract the bucket from engagement with the ground but will tend to replace that force which has been urging the prime mover and digger as a whole rearwardly, this force being a reaction force to the attempted digging stroke of the bucket teeth. The sudden release of this force will allow the prime mover and digger to rock forwardly, followed by an abrupt recurrent rearward movement upon the re-activation of the solenoid coil 65 and the application of digging force to the bucket 24. As 'a esult of this rocking' notion of the prime mover and the digger, it has been found that the lpenetration characteristics of the digger bucket are greatly improved, particularly when operating .in extremely hard soil or asphalt or macadam surfaces. In fact,.this improved digging ability has made possible the utilization of a digger of this type for the first time in the digging. of macadam roads.

The action will continue so long as the motor 75 runs' and the manual switch 77 remains closed. For digging in loose soil or under normal operating conditions, it is often undesirable to utilize the oscillation means hereinbefore described, and the oscillation means may be readily rendered inoperative by merely opening the switch 77.

In the embodiment of the invention illustrated in FIG- URE 3 of the drawings, lines 49 and 57 refer to the same lines 49 and 57 described in connection with FIGURE 2 and are effective for conveying iluid under pressure and relief uid, respectively, from the valve block 42. In the embodiment of FIGURE 3, the double crowd cylinders 28 are subjected to oscillatory action in order to obtain the same digging characteristics as hereinbefore described in connection with the actuating cylinder 30. Obviously, the same apparatus illustrated in FIGURE 2 may be utilized for the actuation of the crowd cylinders 2S, and equally obviously, the oscillating mechanism disclosed in FIGURE 3 can be utilized in connection with the actuating cylinder 30.

As illustrated in FIGURE 3, a four-way pilot operated valve 80 is utilized as the primary oscillating member, this valve being provided with a central land 81 and terminal lands 82 and `83, respectively, snugly iitting within the valve chamber 84. The line 49 is adapted to communicate with lines 85 and 85a leading to the blind ends of the crowd cylinders 28 for displacing the crowd cylinder pistons 27a to the right, thereby extending the crowd cylinder pistons 27b, such displacement of the rods 27b urging the bucket teeth 25 into the digging medium. The rod ends of the cylinders 28 are interconnected with the valve chamber 84 through lines 86 and 36a. Line 57 is branched as at 57a and 57b t-o provide drain lines adjacent the lands 82 and 83, respectively, of the valve body `80.

A coil compression spring 87 acts on the valve body 89 to urge it in a righthand direction, i.e. to the position illustrated in FIGURE 3 of the drawings. A spring pressed sequence valve 90 is provided in proximity to the valve chamber 84, the sequence valve 90 having an elongated stem 91 projecting into the fluid passage 92 communicating with the line `49 and with a second line 93 leading to the blind righthand end of the valve body, i.e. the end provided by the land 83. A threaded restrictor valve 94 is provided in the line 93, the restrictor valve 94 being adjustable to control the bypassing of fluid from the line `93 to drain, as through line 95.

Assuming now that the control valve handle 15 has been moved so as to interconnect line 49 with the fluid pressure supply line 4t)I and to interconnect the drain line 57 with the main drain line 48, iluid under pressure within line 49 is introduced into the lefthand end of the cylinders 28 through the lines 85 and 85a. The other ends of the cylinders 28 are drained through lines 86 and 86a, line 57h and line 57. Consequently, the crowd cylinders are extended and the bucket teeth 25 are urged into engagement with the ground. When suicient resistance to further displacement of the pistons 27a is encountered, the pressure within the line 49 rises until it overcomes the compression force of the spring 96, which compression force normally urges the valve 90 to the right to maintain the valve stem 9.1 in the passage 92. When the pressure upon the end of the valve stem 91 exerted by pressure in the line 49 becomes sucient, the stem 91 is moved rearwardly and lluid pressure from the line 49 can now be exerted upon the land 83 of the valve body 80 through the lines 92 and 93. This fluid pressure becomes suicient to overcome the bias of the spring 87, thusv displacing the valve body 80 to the left.

The displacement of the valve body 80 to the left opens lines 85-8'5a to drain line 57a between valve lands 81 and 82, and concurrently pressures line 86-86a thru line 49 between valve lands 81 and 83.

To maintain the valve body 80 in its leftward position, pressure must be constantly exerted upon the blind end of the valve body through the line 93. However, the restricted bleed valve 94 meters fluid from the line 93 into the drain line 95. The loss of fluid through the valve `94 will cause a reduction in the magnitude of pressure in the line 93. When this pressure has dropped to a Value less than that necessary to maintain the valve body 80 in its leftward position, the spring 87 will return the valve body S0 to the position illustrated in FIGURE 3. At the same time, there is substantially no resistance to movement of the crowd cylinder pistons 27a to the left under the influence of pressure exerted through the lines 86 and 86a, and consequently the pressure in the line 49 will `drop to line pressure. This line pressure will not be sufficient to overcome the resistance of the pressure spring 96, and the valve stem 92 will be shifted until the valve stem occupies its position shown in FIGURE 3 at which line 93 is cut off from the line 49.

Thus, the only pressure present in line 93 will be that trapped therein by the subsequent movement of the valve stem 91 to its position of FIGURE 3, and this pressure will be bled off through the restrictor valve 94. It will be readily understood that the frequency of the cycle depends upon the amount of pressure bled through the restrictor valve l94 and threaded adjustment of this valve into the drain line 95 will determine the frequency with which the valve body 80 is reciprocated.

Thus, it will be appreciated that the embodiment of FIGURE 3 provides a hydraulic system whereby the bucket may be rapidly reciprocated or oscillated toward and away from the ground. Actually, the cycle is repeated with such rapidity that the teeth 2'5 are never out of contact with the ground and the effect of reciprocation of the valve body 80 will be the rocking back and forth of the tractor and digger assembly in the manner hereinbefore described in connection with the embodiment of FIGURE 2.

Therefore, the present invention provides a new and novel apparatus for rapidly oscillating the digging elements of a digger in such manner that the digger and prime mover assembly are oscillated at a predetermined frequency. If this frequency is attuned to the natural vibration or oscillation frequency of the assembly, a cumulative oscillation elfect is obtained and the oscillation may be continued with the consumption of a remarkably small amount of power. Further, when a harmonic situation obtains, the digging efficiency of the assembly is greatly enhanced, as attested by the fact that an assembly provided with the apparatus 0f this invention may, for the first time, be utilized in the destruction of macadam or concrete roads, driveways or the like.

What I claim to be my invention is:

l. In a digger assembly having a prime mover, a boom secured to the prime mover for movement relative thereto, and a dipper carried by the boom, the improvements of hydraulic means for actuating said dipper relative to said boom, an oscillation valve forming a part of said hydraulic means, and means for oscillating said valve at a predetermined regular frequency correlated with the resonant mechanical frequency of the digging assembly.

2. An apparatus for oscillating a dipper of a digger assembly carried by a prime mover, comprising hydraulic means for actuating said dipper into contact with the ground, an oscillatable valve incorporated in said hydraulic means, means for oscillating said valve at a regular frequency correlated with the natural resonant mechanical frequency of the digger assembly and prime mover, and means for varying the oscillation frequency of the valve.

3. In a digger of the type wherein an actuating cylinder is utilized to actuate a digging bucket into ground-engaging contact, the bucket being carried by a dipstick and boom assembly supported from a prime mover, the improvements of means for actuating said actuating assembly at a predetermined regular frequency and in opposite directions to alternately urge said bucket against and away from the ground, comprising means for supplying hydraulic fluid to opposing ends of said cylinder, an oscillatable valve disposed in the path of hydraulic fluid flow to said opposite ends of said cylinder, and means for oscillating said valve on the order of 251/2 times per second.

4. In combination with a digger assembly having a vertically swingable boom, a dipper stick swingably mounted on the outer end of said boom and a dipper mounted in the end of said dipper stick, means mounting said digger assembly including a prime mover, power transmitting means operatively interconnecting said prime mover and said digger assembly, and means driven by said prime mover for oscillating said dipper relative to said mounting means at a regular frequency correlated with the resonant mechanical frequency of the mounting means and digger assembly.

5. The combination set forth in claim 4 wherein said oscillating means comprises a source of pressure fluid, a hydraulic motor operatively connected to said dipper and means for automatically sequentially reversing the pressure lluid flow to said motor.

6. In combination with a digger assembly including a swingable boom, a dipper stick swingably mounted on said boom and a dipper swingably mounted on one end of said dipper stick, fluid pressure actuated means for swinging said boom, dipper stick and dipper respectively, and means operably associated with said lluid pressure means for oscillating said dipper relatively to said boom in timed sequence, comprising an oscillation valve and means for oscillating said valve including a spring urging said valve in one direction, a solenoid for selectively urging said valve in the opposite direction and switch means for intermittently energizing said solenoid.

References Cited in the tile of this patent UNITED STATES PATENTS 1,812,925 Buckland July 7, 1931 A1,840,002 Wallis Jan. 5, 1932 2,303,852 Linn Dec. 1, 1942 2,606,013 Acker Aug. 5, 1952 2,639,023 Goodrich May l19, 1953 2,698,697 Holopainen Jan. 4, 1955 2,735,255 Harper Feb. 2l, 1956 2,784,855 Acker Mar. 12, 1957 FOREIGN PATENTS 401,265 Italy Jan. 14, 1943 

1. IN A DIGGER ASSEMBLY HAVING A PRIME MOVER, A BOOM SECURED TO THE PRIME MOVER FOR MOVEMENT RELATIVE THERETO, AND A DIPPER CARRIED BY THE BOOM, THE IMPROVEMENTS OF HYDRAULIC MEANS FOR ACTUATING SAID DIPPER RELATIVE TO SAID BOOM, AN OSCILLATION VALVE FORMING A PART OF SAID HYDRAULIC MEANS, AND MEANS FOR OSCILLATING SAID VALVE AT A PREDETERMINED REGULAR FREQUENCY CORRELATED WITH THE RESONANT MECHANICAL FREQUENCY OF THE DIGGING ASSEMBLY. 